The hydroformylation reaction, also known as the oxo reaction, is used extensively in commercial processes for preparing aldehydes by reacting one mole of an olefin with one mole each of hydrogen and carbon monoxide. The most extensive use of the reaction is in the preparation of normal- and iso-butyraldehyde from propylene.
The ratio of the amount of the normal-aldehyde product to the amount of the iso-aldehyde product typically is referred to as the normal to iso (N:I or N/I) or the normal to branched (N:B or N/B) ratio.
In the case of propylene, the normal- and iso-butyraldehydes obtained from propylene are, in turn, converted into many commercially valuable chemical products, such as, for example, n-butanol, 2-ethyl-hexanol, n-butyric acid, iso-butanol, neo-pentyl glycol, 2,2,4-trimethyl-1,3-pentanediol, and the mono-isobutyrate and di-isobutyrate esters of 2,2,4-trimethyl-1,3-pentanediol. The hydroformylation of higher α-olefins (such as 1-octene, 1-hexene, and 1-tetradecene) yields aldehyde products that are useful feedstocks for preparing detergent alcohols and plasticizer alcohols.
U.S. Pat. No. 5,840,647 and U.S. Pat. No. 6,130,358 introduced a new concept in ligand design with the disclosure of halogen substituents on the phosphorus atom of trivalent phosphorus ligands. These halogenated phosphorus ligands are readily prepared, possess high activity and good stability, and permit a wide N/I range of products to be prepared by simply varying the process parameters.
Many of the halophosphite ligand compositions contain the phosphorus atom in a macrocyclic ring structure. Macrocyclic rings introduce the possibility of many different structural and conformational isomers of the phosphorus ligands. The presence of a plurality of isomeric forms of the phosphorus ligand can be problematic, because each of the different isomers can form complexes with the transition metal catalyst, and the reactivity and selectivity of the catalyst can vary greatly depending on which isomeric form of the phosphorus ligand is attached to the transition metal atom. Frequently, using mixed isomeric forms of the phosphorus ligand results in a complex catalyst composition, which makes it difficult to predict and control the activity and selectivity of the catalyst.
Thus, it is desirable to be capable of creating a catalyst composition from a mixture of phosphorus ligand isomers that behaves in a manner as if it were a single isomer of the phosphorus ligand. In addition or alternatively, it is desirable to have a process by which a single isomer can be isolated from a mixture of isomers.
The present invention addresses these desires as well as others, which will become apparent from the following description and the appended claims.